1. Field of the Invention
This invention generally relates to a bicycle bottom bracket assembly. More specifically, the present invention relates to a bicycle bottom bracket assembly having sealing structure that prevents water from reaching a bearing unit.
2. Background Information
Generally speaking, a conventional bicycle has a pair of wheels mounted to a main frame formed of a plurality of tubes and a front fork pivotally connected to the main frame. The tubes of the main frame typically include a top tube, a down tube, a head tube, a seat tube, a pair of seat stays, a pair of chain stays and a cylindrical or tubular hanger part.
The cylindrical or tubular hanger part of the frame is often called a bicycle bottom bracket hanger because it supports a bottom bracket. Many different types of bottom brackets are currently available on the market. Generally speaking, a conventional bicycle bottom bracket has a pair of bearings mounted into a tubular hanger part of a bicycle frame for rotatably supporting a crank axle. One type of a conventional bottom bracket assembly is disclosed in U.S. Pat. No. 6,983,672. This conventional bottom bracket assembly is equipped with first and second axle support members that have first and second bearings, respectively. The first and second axle support members are screwed into both end portions of the hanger part separately. The crank axle is rotatably supported on both of the first and second bearings, and right and left cranks are non-rotatably mounted on the both axial end portions of the crank axle. Sometimes the first and second axle support members are press-fitted in to both end portions of the hanger part. In some cases, a dust tube (e.g., a connecting tube) is provided to prevent contamination such as water, muddy water and so on from intruding from the bottom bracket hanger part of the bicycle frame into the bearing units. One example of a conventional crank axle assembly with a dust tube (e.g., a connecting tube) is disclosed in U.S. Pat. No. 7,503,700.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle bottom bracket assembly. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.